| Abstrakt: |
The yields of tris(2,4-pentanedionato)chrvmium(III) (Cr(acac)) formed in the presence of either the ammonia (Am), ethanoate (ET), trichloroethanoate (TCE), or trifluoroethanoate (TFE) ligand in high pH aqueous solution, were compared with those from a medium containing only hydroxyl and water as the principal ligands besides the acac. The presence of Am, ET, and TCE drastically reduced the yields at pH's 9.5-10.5, 7.5-9.0/9.5-11.0, and 9.0-12.0, respectively in increasing order ET > Am < TCE. The role of Am is attributed mainly to the oxo-bridged species ((OH)(HO)AmCr(O)(OH)CrAm(HO)(OH)) (1), ((OH)(HO)AmCr(O)CrAm(HO)(OH)) (2), and ((OH)(HO)AmCr(O)(OH)CrAm(HO)(OH)) (3). 2 is the most deactivating species mainly on the basis that the Cr-O bond of the oxo-bridge is suggested as being stronger than the Cr-O bond of the hydroxo-bridge. As for ET and TCE, oxo-bridged polymeric ethanoato- and trichloroethanoatochromium(III) species are also proposed as the main origin of the drastic deactivation of the reaction not observed for TFE due possibly, to the insignificance of oxo-bridges in tnfluoroethanoatochromium(III) species. [ABSTRACT FROM AUTHOR] |
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